1. Technical Field
The present invention relates to a technology of ejecting a liquid, which is received in a container, from ejecting nozzles provided in an ejecting head.
2. Related Art
There is known a liquid ejecting apparatus including an ejecting head for ejecting a liquid which is received in a container. The ejecting head of the liquid ejecting apparatus is provided therein with a liquid chamber supplied with the liquid, and ejecting nozzles for ejecting the liquid. If a pressurizing mechanism provided in the liquid chamber is driven to pressurize the liquid, the liquid is ejected from the ejecting nozzles. Since the liquid is ejected in the above manner, if bubbles mixed and supplied with the liquid are accumulated in the liquid chamber, the liquid in the liquid chamber is not able to be appropriately pressurized, and thus it is difficult to eject the liquid from the ejecting nozzles. In addition, in order to be able to eject a lot of liquid at a time, a liquid ejecting apparatus has been developed to supply the liquid from the container to a plurality of ejecting heads and eject the liquid from the ejecting heads at the same time. However, in such a liquid ejecting apparatus, circumstances in which the bubbles are accumulated in the liquid chamber occur more easily as the ejecting heads are increased. Accordingly, the liquid ejecting apparatus including the plurality of ejecting heads for ejecting the liquid employs a configuration, in which the liquid supplied to the ejecting heads is not collected in the ejecting heads until the fluid is ejected, but the fluid is circulated in an inside and an outside of the ejecting heads by discharging the fluid outward from the ejecting heads and again supplying it into the ejecting heads so as not to accumulate the bubbles in the liquid chamber.
In addition, in the configuration for circulating the liquid in the liquid ejecting apparatus including the plurality of ejecting heads, as described above, a structure in which the ejecting heads are connected in series to each other, and a structure in which the ejecting heads are connected in parallel to each other, are proposed. Here, the expression “structure in which the ejecting heads are connected in series to each other” means that the liquid circulated in any ejecting head and then discharged outward from the ejecting head is supplied to the ejecting head at a downstream side, so that the liquid is circulated in sequence in the plurality of ejecting heads. In addition, the expression “structure in which the ejecting heads are connected in parallel to each other” means that a passage for circulating the liquid is branched along the way, and thus the plurality of ejecting heads are connected in parallel to each other, so that the liquid is independently circulated in each ejecting head.
In the structure in which the ejecting heads are connected in series to each other, a pressure difference between the pressure of the liquid supplied to the ejecting heads located at the upstream side and the pressure of the liquid supplied to the ejecting head located at the downstream side is increased due to the pressure loss occurring in the ejecting heads. As a result, it is difficult to reliably eject the liquid from each of the ejecting heads. Meanwhile, in the structure in which the ejecting heads are connected in parallel to each other, due to influences, such as a difference in the shape or length of the passages for circulating the liquid or the like, ejecting heads which can easily circulate the liquid therein and ejecting heads which have difficulty circulating the liquid therein can be generated. In the case where the ejecting heads which have difficulty circulating the fluid are generated, it is difficult to discharge the bubbles from the interior of the ejecting heads.
Accordingly, there is provided a technology capable of being shifted between the state where the plurality of ejecting heads are connected in series to each other and the state where the plurality of ejecting heads are connected in parallel to each other, in which when the liquid is ejected, the plurality of ejecting heads are connected in parallel to each other, while when the bubbles are discharged, the plurality of ejecting heads are connected in series to each other (JP-A-2008-246843).
However, since the state where the plurality of ejecting heads are connected in series to each other and the state where the plurality of ejecting heads are connected in parallel to each other are shifted between in the proposed technology, a complicated configuration is needed. In addition, since the flow passage of the fluid has a complicated shape, the passage resistance is increased. In addition, a switching structure is added, and thus the passage resistance is further increased. Furthermore, since the plurality of ejecting heads are connected in series to each other when the liquid is circulated, the passage resistance is gradually increased. As a result, there is a problem that since a huge load is exerted on a circulation pump, a circulation pump with a large capacity is needed.